Triple lead bone screw

ABSTRACT

Pedicle screw assemblies and related bone screws. In some embodiments, the bone screw may comprise a head portion and an axial shaft. The axial shaft may comprise a threaded portion comprising a triple lead thread disposed about the axial shaft. The axial shaft may further comprise a tapering portion and a non-tapering portion. The tapering portion may comprise multiple tapering portions tapering at differing rates, and may be positioned adjacent to a tip of the axial shaft. Each of the three leads may extend coextensively along at least a majority of the length of the axial shaft, the threaded portion, the tapering portion, and/or the non-tapering portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No.12/818,749, filed on Jun. 18, 2010, and titled “TRIPLE LEAD BONE SCREW,”which claims the benefit of U.S. Provisional Patent Application No.61/218,574, filed on Jun. 19, 2009, and also titled “TRIPLE LEAD BONESCREW.” Both of the aforementioned applications are incorporated byreference herein in their entireties.

FIELD OF THE INVENTION

The present invention relates generally to a triple lead bone screw foruse in surgical applications. More specifically, the present inventionrelates to a triple lead bone screw for use in spinal surgicalapplications, such as pedicle screw applications and the like.

BACKGROUND OF THE INVENTION

Triple lead screws are used in a variety of applications, including bonescrew applications. These screws utilize three thread starts/leadsbetween the distal end (i.e. tip) of the screw and the proximal end(i.e. head) of the screw. The three thread starts are typically spacedapart by about 120 degrees. The screws may be used to engage bone, or,more often, the triple lead portion is used to engage an anatomicalplate or other implant structure. The advantage of triple lead screwsrelative to single or double lead screws is that triple lead screws areadvanced farther with fewer turns, i.e. they are placed more quickly andwith less effort. The disadvantage of triple lead screws relative tosingle or double lead screws is that triple lead screws typically have alower pullout or backout strength, i.e. they may become dislodged moreeasily and with less effort.

What is still needed in the art is a triple lead pedicle screw or thelike that overcomes the above mentioned disadvantage.

BRIEF SUMMARY OF THE INVENTION

In various exemplary embodiments, the present invention provides atriple lead pedicle screw or the like that is capable of being placedquickly with minimal effort and that resists pullout or backout at leastas effectively as comparable single or double lead screws. This triplelead bone screw is ideally suited for the surgical correction of spinaldeformities and other similar surgical procedures in which multiplescrews must be placed. In such surgical procedures, a surgeon may become fatigued and time is of the essence.

In one exemplary embodiment, the present invention provides a pediclescrew assembly, including: a bone screw having a head portion and athread portion, wherein the thread portion includes an axial shaft and atriple lead thread disposed about the axial shaft; and a rod retentionmember selectively coupled to the head portion of the bone screw.Optionally, the triple lead thread of the thread portion of the bonescrew includes leads that start with about 120 degrees of separation.Optionally, the triple lead thread of the thread portion of the bonescrew includes leads that originate at different points along the axialshaft of the thread portion of the bone screw. Optionally, the triplelead thread of the thread portion of the bone screw includes leads thatterminate at different points along the axial shaft of the threadportion of the bone screw. Optionally, the axial shaft of the threadportion of the bone screw includes a first tapering portion proximate atip of the axial shaft of the thread portion of the bone screw.Optionally, the axial shaft of the thread portion of the bone screwincludes a second tapering portion proximate the tip of the axial shaftof the thread portion of the bone screw. Preferably, the second taperingportion tapers more steeply than the first tapering portion. Optionally,the axial shaft of the thread portion of the bone screw includes areduced diameter portion proximate the head portion of the bone screw.Optionally, the axial shaft of the thread portion of the bone screwincludes one or more tapering portions proximate the head portion of thebone screw. Preferably, the rod retention member is selectivelypivotably coupled to the head portion of the bone screw.

In another exemplary embodiment, the present invention provides a bonescrew, including: a head portion; and a thread portion, wherein thethread portion includes an axial shaft and a triple lead thread disposedabout the axial shaft. Optionally, the triple lead thread of the threadportion of the bone screw includes leads that start with about 120degrees of separation. Optionally, the triple lead thread of the threadportion of the bone screw includes leads that originate at differentpoints along the axial shaft of the thread portion of the bone screw.Optionally, the triple lead thread of the thread portion of the bonescrew includes leads that terminate at different points along the axialshaft of the thread portion of the bone screw. Optionally, the axialshaft of the thread portion of the bone screw includes a first taperingportion proximate a tip of the axial shaft of the thread portion of thebone screw. Optionally, the axial shaft of the thread portion of thebone screw includes a second tapering portion proximate the tip of theaxial shaft of the thread portion of the bone screw. Preferably, thesecond tapering portion tapers more steeply than the first taperingportion. Optionally, the axial shaft of the thread portion of the bonescrew includes a reduced diameter portion proximate the head portion ofthe bone screw. Optionally, the axial shaft of the thread portion of thebone screw includes one or more tapering portions proximate the headportion of the bone screw.

In a further exemplary embodiment, the present invention provides a bonescrew, including: a head portion; and a thread portion, wherein thethread portion includes an axial shaft and a triple lead thread disposedabout the axial shaft, wherein the axial shaft of the thread portion ofthe bone screw includes a first tapering portion proximate a tip of theaxial shaft of the thread portion of the bone screw, and wherein theaxial shaft of the thread portion of the bone screw includes a secondtapering portion proximate the tip of the axial shaft of the threadportion of the bone screw, wherein the second tapering portion tapersmore steeply than the first tapering portion. Optionally, the triplelead thread of the thread portion of the bone screw includes leads thatoriginate at different points along the axial shaft of the threadportion of the bone screw. Optionally, the triple lead thread of thethread portion of the bone screw includes leads that terminate atdifferent points along the axial shaft of the thread portion of the bonescrew. Optionally, the axial shaft of the thread portion of the bonescrew includes a reduced diameter portion proximate the head portion ofthe bone screw. Optionally, the axial shaft of the thread portion of thebone screw includes one or more tapering portions proximate the headportion of the bone screw.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated and described herein with referenceto the various drawings, in which like reference numbers are used todenote like screw components, as appropriate, and in which:

FIG. 1 is a planar side view of one exemplary embodiment of the triplelead pedicle screw assembly of the present invention, including thetriple lead bone screw of the present invention and an associated rodretention member;

FIG. 2 is a perspective view of the triple lead pedicle screw assemblyof FIG. 1;

FIG. 3 is a perspective view of one exemplary embodiment of the bonescrew of the present invention;

FIG. 4 is a planar side view of the bone screw of FIG. 3;

FIG. 5 is another planar side view of the bone screw of FIG. 3;

FIG. 6 is a perspective view of another exemplary embodiment of the bonescrew of the present invention;

FIG. 7 is a planar side view of the bone screw of FIG. 6; and

FIG. 8 is another planar side view of the bone screw of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

Again, in various exemplary embodiments, the present invention providesa triple lead pedicle screw or the like that is capable of being placedquickly with minimal effort and that resists pullout or backout at leastas effectively as comparable single or double lead screws. This triplelead bone screw is ideally suited for the surgical correction of spinaldeformities/anomalies/trauma and other similar surgical procedures inwhich multiple screws must be placed. In such surgical procedures, asurgeon may be come fatigued and operative time is of the essence.

Referring to FIGS. 1 and 2, in one exemplary embodiment, the triple leadpedicle screw assembly 10 of the present invention includes a triplelead bone screw 12 and a rod retention member 14.

The triple lead bone screw 12 includes a head portion 16 and a threadedportion 18. The head portion 16 of the triple lead bone screw 12consists of an enlarged structure, such as a wholly or partiallyspherical structure, a wholly or partially cylindrical structure, or thelike, having one or more tool receiving recesses 20 manufactured intothe top surface thereof, by which the triple lead bone screw 12 isgrasped and/or turned. Optionally, three such tool receiving recesses 20are utilized and are spaced apart by about 120 degrees, although it willbe readily apparent to those of ordinary skill in the art that othersuitable configurations may be utilized. The threaded portion 18 of thetriple lead bone screw 12 consists of three thread starts/leads betweenthe distal end (i.e. tip) 22 of the screw 12 and the proximal end (i.e.head) 24 of the screw 12. Optionally, the three thread starts are spacedapart by about 120 degrees, although it will be readily apparent tothose of ordinary skill in the art that other suitable configurationsmay be utilized. Optionally, the three thread starts/leads alsooriginate and/or terminate at different positions along the length ofthe screw 12. In other words, the three thread starts/leads may or maynot coincide along the length of the screw 12 and may be spaced apart byany desired constant or variable distance. Finally, one or more of thethree thread starts/leads may be selectively broken or notched to createa biting surface, such as near the tip 22 of the screw 12 so that thescrew will advance into bone from the first tum. Any suitable thickness,pitch, or other dimensions may be utilized, as well as any suitablematerials (e.g. a biocompatible metal, ceramic, or plastic, bonymaterial, etc.).

The rod retention member 14 consists of a U-shaped member 26 having ahole in the bottom. The threaded portion 18 of the bone screw 12 isdisposed through this hole, with the head portion 16 of the bone screwbeing pivotably seated in the interior bottom of the U-shaped member,prior to the screw 12 being driven into bone. The rod retention member14 includes a plurality of internally threaded, concentrically arranged,vertically extending arm members 28 between which a stabilizing rod orother similar stabilizing structure (not illustrated) is selectivelydisposed. This stabilizing rod is then “locked” into place via theengagement of an externally threaded cap (not illustrated) into theinternal threads of the arm members 28, thereby “locking” theorientation of the rod retention member 14 with respect to the headportion 16 of the triple lead bone screw 12, as the stabilizing rod isin direct or indirect contact with the head portion 16 of the triplelead bone screw 12. It will be readily apparent to those of ordinaryskill in the art that various other structures may also be disposedbetween the stabilizing rod and either or both of the externallythreaded cap and the head portion 16 of the triple lead bone screw 12.In this manner, screws 12 may be placed in different anatomicalstructures, or different parts of the same anatomical structure, andsecurely joined by stabilizing structures in a predeterminedconfiguration and alignment.

Referring to FIGS. 3-5, in one exemplary embodiment, the triple leadbone screw 12 of the present invention includes a head portion 16 and athreaded portion 18. The head portion 16 of the triple lead bone screw12 consists of an enlarged structure, such as a wholly or partiallyspherical structure, a wholly or partially cylindrical structure, or thelike, having one or more tool receiving recesses 20 manufactured intothe top surface thereof, by which the triple lead bone screw 12 isgrasped and/or turned. Optionally, three such tool receiving recesses 20are utilized and are spaced apart by about 120 degrees, although it willbe readily apparent to those of ordinary skill in the art that othersuitable configurations may be utilized. The threaded portion 18 of thetriple lead bone screw 12 consists of three thread starts/leads betweenthe distal end (i.e. tip) 22 of the screw 12 and the proximal end (i.e.head) 24 of the screw 12. Optionally, the three thread starts are spacedapart by about 120 degrees, although it will be readily apparent tothose of ordinary skill in the art that other suitable configurationsmay be utilized. Optionally, the three thread starts/leads alsooriginate and/or terminate at different positions along the length ofthe screw 12. In other words, the three thread starts/leads may or maynot coincide along the length of the screw 12 and may be spaced apart byany desired constant or variable distance. Finally, one or more of thethree thread starts/leads may be selectively broken or notched to createa biting surface, such as near the tip 22 of the screw 12 so that thescrew will advance into bone from the first tum. Any suitable thickness,pitch, or other dimensions may be utilized, as well as any suitablematerials (e.g. a biocompatible metal, ceramic, or plastic, bonymaterial, etc.).

Referring specifically to FIG. 5, the threaded portion 18 of the screw12 includes an axial shaft 30 that may have a non-tapering portion 32, afirst tapering portion 34, and a second tapering portion 36 disposed, inorder, between the head portion 16 of the screw 12 and the rounded orpointed tip 38 of the screw 12. Preferably, the taper of the secondtapering portion 36 is greater than the taper of the first taperingportion 34, with the second tapering portion sweeping a 45-degree arc, a60-degree arc, etc. The threads are disposed about these varioussegments of the screw 12.

Referring to FIGS. 6-8, in another exemplary embodiment, the triple leadbone screw 12 of the present invention includes a head portion 16 and athreaded portion 18. The head portion 16 of the triple lead bone screw12 consists of an enlarged structure, such as a wholly or partiallyspherical structure, a wholly or partially cylindrical structure, or thelike, having one or more tool receiving recesses 20 manufactured intothe top surface thereof, by which the triple lead bone screw 12 isgrasped and/or turned. Optionally, three such tool receiving recesses 20are utilized and are spaced apart by about 120 degrees, although it willbe readily apparent to those of ordinary skill in the art that othersuitable configurations may be utilized. The threaded portion 18 of thetriple lead bone screw 12 consists of three thread starts/leads betweenthe distal end (i.e. tip) 22 of the screw 12 and the proximal end (i.e.head) 24 of the screw 12. Optionally, the three thread starts are spacedapart by about 120 degrees, although it will be readily apparent tothose of ordinary skill in the art that other suitable configurationsmay be utilized. Optionally, the three thread starts/leads alsooriginate and/or terminate at different positions along the length ofthe screw 12. In other words, the three thread starts/leads may or maynot coincide along the length of the screw 12 and may be spaced apart byany desired constant or variable distance. Finally, one or more of thethree thread starts/leads may be selectively broken or notched to createa biting surface, such as near the tip 22 of the screw 12 so that thescrew will advance into bone from the first tum. Any suitable thickness,pitch, or other dimensions may be utilized, as well as any suitablematerials (e.g. a biocompatible metal, ceramic, or plastic, bonymaterial, etc.).

Referring specifically to FIG. 8, the threaded portion 18 of the screw12 includes an axial shaft 30 that may have a non-tapering portion 32, afirst tapering portion 34, and a second tapering portion 36 disposed, inorder, between the head portion 16 of the screw 12 and the rounded orpointed tip 38 of the screw 12. Preferably, the taper of the secondtapering portion 36 is greater than the taper of the first taperingportion 34, with the second tapering portion sweeping a 45-degree arc, a60-degree arc, etc. The threads are disposed about these varioussegments of the screw 12. In this exemplary embodiment, a reduceddiameter portion 40 and one or more tapering portions 42 are alsodisposed along the axial shaft 30 between the head portion 16 and thethreaded portion 18 of the screw 12.

Axial pullout testing of the triple lead bone screw 12 of the presentinvention demonstrated performance comparable to that of a conventionalsingle lead bone screw.

Although the present invention has been illustrated and described hereinwith reference to preferred embodiments and specific examples thereof,it will be readily apparent to those of ordinary skill in the art thatother embodiments and examples may perform similar functions and/orachieve like results. All such equivalent embodiments and examples arewithin the spirit and scope of the present invention, are contemplatedthereby, and are intended to be covered by the following claims.

1. A pedicle screw assembly, comprising: a bone screw comprising a headportion and a threaded portion, wherein the threaded portion comprisesan axial shaft and a triple lead thread disposed about the axial shaft,wherein the axial shaft comprises a tapering portion and a non-taperingportion, wherein the tapering portion is positioned adjacent to a tip ofthe axial shaft, wherein the triple lead thread comprises three distinctthread leads, wherein each of the three leads terminates at a differentpoint along a tapering portion of the axial shaft, and wherein each ofthe three leads extends coextensively along at least a majority of thelength of the threaded portion; and a rod retention member selectivelycoupled to the head portion of the bone screw.
 2. The pedicle screwassembly of claim 1, wherein the rod retention member comprises aU-shaped member comprising a hole for receiving the head portion of thebone screw.
 3. The pedicle screw assembly of claim 2, wherein the headportion is configured to be pivotably seated in the U-shaped member. 4.The pedicle screw assembly of claim 1, wherein each of the three leadsextends coextensively along at least substantially the entire length ofthe threaded portion.
 5. The pedicle screw assembly of claim 1, whereinthe axial shaft further comprises a second tapering portion.
 6. Thepedicle screw assembly of claim 5, wherein the second tapering portionis positioned between the tapering portion and the non-tapering portion.7. The pedicle screw assembly of claim 6, wherein the tapering portiontapers more steeply than the second tapering portion.
 8. The pediclescrew assembly of claim 5, wherein at least one of the three leadsterminates at a point along the second tapering section.
 9. A bonescrew, comprising: a head portion; and a threaded portion, wherein thethreaded portion comprises an axial shaft and a triple lead threaddisposed about the axial shaft, wherein the axial shaft comprises atapering portion and a non-tapering portion, wherein the taperingportion is positioned adjacent to a tip of the axial shaft, wherein thetriple lead thread comprises three distinct thread leads, wherein atleast two of the three leads terminate at a different points along thetapering portion of the axial shaft, and wherein each of the three leadsextends coextensively along at least a majority of the length of theaxial shaft.
 10. The bone screw of claim 9, wherein at least one of thethree thread leads comprises a biting surface.
 11. The bone screw ofclaim 10, wherein each of the three thread leads comprises a bitingsurface.
 12. The bone screw of claim 10, wherein the biting surfacecomprises a notch formed within the at least one of the three threadleads.
 13. The bone screw of claim 9, wherein the three thread leadsstart with about 120 degrees of separation.
 14. The bone screw of claim9, wherein at least one of the three thread leads originates at adifferent point along the threaded portion than the other two threadleads.
 15. The bone screw of claim 9, wherein the axial shaft furthercomprises a reduced diameter portion, and wherein the reduced diameterportion is positioned adjacent to the head portion.
 16. The bone screwof claim 9, wherein the axial shaft further comprises a second taperingportion.
 17. The bone screw of claim 16, wherein the second taperingportion is positioned between the tapering portion and the non-taperingportion.
 18. The bone screw of claim 16, wherein the tapering portiontapers more steeply than the second tapering portion.
 19. The bone screwof claim 9, wherein each of the three leads terminates at a differentpoint along the tapering portion of the axial shaft.
 20. A bone screw,comprising: a head portion; an axial shaft; and a tip, wherein the axialshaft comprises a tapering portion and a non-tapering portion, whereinthe axial shaft further comprises a triple lead thread disposed aboutthe axial shaft, wherein the triple lead thread comprises three distinctthread leads, wherein the tapering portion is positioned adjacent to thetip, and wherein each of the three leads extends coextensively along atleast a majority of the length of the non-tapering portion.